Since e90's are just coming out of warranty
The experience level even at a good Indy shop isn't that high yet.
Mine changed my radiator fluid but they took the time to read the new
procedures . Sounds like this one got a bad part and it failed if there hadn't been a programming update at the same time the issue wouldn't have been as confusing. Its good to know about the serial bus causing multiple errors.
Thanks for the report.